1. Field of the Invention
The present invention relates to a hydrolytic condensation coating composition, a hard coat film formed from the coating composition, and a method for preparing the hard coat film, more particularly to an epoxy-resin-based coating composition that includes silane as a coupling agent, and a coat film with high transparency and hardness and obtained by coating a transparent plastic substrate with the coating composition, followed by a thermo-curing process.
2. Description of the Related Art
With the consideration of formability and reduction in weight, there is a trend to gradually replace glass products with plastic products. However, plastic products typically have surfaces which can be easily scratched. A hard coat film has been proposed heretofore for application to a surface of a plastic product so as to impart the product with enhanced anti-scratch and anti-abrasion characteristics. The hard coat film is typically obtained by coating a plastic substrate with a thermosetting resin or an ionizing radiation curing resin (such as UV hard resin).
U.S. Pat. No. 6,376,060B1 discloses a hard coat produced from a coating component containing one or more organic components having a polymerizable functional group and an inorganic filler, at least one of the organic components being free from a hydrogen bond-forming group. U.S. Patent Publication No. 2002/0028328A1 discloses an anti-glare hard coat film which comprises 100 parts by weight of (A) a resin cured by an ionizing radiation, 2˜25 parts by weight of (B) silica particles having an average diameter of 0.5 to 5 μm, and 100˜200 parts by weight of (C) fine particles having an average diameter of 1˜60 nm. U.S. Pat. No. 6,329,041B1 discloses a hard coat film which comprises a plastic base film having a pencil hardness from 4 B to HB, a buffer layer composed of one or a plurality of layers with a total thickness of 3˜50 μm formed on at least one side of the plastic base film, a hard coat layer (formed from an ionizing radiation curing resin) with a thickness of 3˜15 μm and a pencil hardness from 3 H to 5 H, and an anti-reflection layer formed on the surface of the hard coat layer. U.S. Pat. No. 5,998,013 discloses an anti-glare hard coat film which comprises a plastic film and a hard coat layer coating the plastic film. The hard coat layer comprises 100 parts by weight of a cured product of a UV-curing resin and 1˜30 parts by weight of agglomerates of colloidal silica particles formed with an amine compound. U.S. Pat. No. 6,319,594 B1 discloses a low-reflection anti-static hard coat film which comprises a transparent conductive layer, a hard coat film and a low-reflection layer formed in sequence on a transparent plastic base film. The hard coat film is formed from an ionizing radiation curing resin composition (optionally containing reactive organic silica compound).
Most of the aforementioned prior art utilize the ionizing radiation (such as UV) curing resin as a main component to form the hard coat film. As the material cost would be relatively high, the aforementioned hard coat films are not suitable for mass production.
U.S. Patent Publication No. 2002/0028312 A1 discloses a hard coat film comprising a silicone-based hard coat layer formed on one side of a multi-layered base which is composed of a plurality of the same or different resin films in a laminate. This kind of hard coat which includes silicone as a main component is relatively brittle. This is a drawback typical of inorganic material. This publication is incorporated herein by reference.
Accordingly, the conventional hard coat film formed either from UV radiation curing resin or from pure siloxane compound suffers from the drawback of higher costs of the UV curing resin material and the UV ionizing radiation equipment, or the drawback of insufficient hardness of the hard coat film, especially that formed from pure siloxane compound. As such, there is a need for a hard coat film that exhibits high transparency and high hardness and that can be produced from low cost materials through a relatively inexpensive method.